It's not a bug. It could happen. Results in game depend on lots of factors, such as injuries, morale, team cohesion, etc. Liverpool are currently 10th in real life and Chelsea are 9th.
I could be wrong, but I think it depends on the country/ league you are playing in. For example, I'm pretty sure U23 coaches can take part in 1st team training in the Premier League. However, some countries/ leagues don't allow this.